1. Field of the Invention
The present invention relates to the art of earthboring. More particularly, the invention relates to methods and apparatus for setting well annulus packers and tool slips, generally, but also specifically when the packer is run in combination with a whipstock.
2. Description of Related Art
The traditional method of directional drilling includes a tapered steel guide for the drill string characterized as a xe2x80x9cwhipstockxe2x80x9d. The whipstock function is to deflect the milling/boring direction of the drill string cutting mill/bit from a previously drilled borehole toward a different, selected direction. Over a length of about 10 to 25 feet, the guide taper of the whipstock deflection surface turns the borehole axis from coincidence with the existing borehole to a deflected line of about 1xc2x0 to about 10xc2x0.
Procedurally, the whipstock is usually secured within an existing borehole casing by a packer/slip tool located along the whipstock length below the bottom end of the deflection surface. The packer is required to seal the existing borehole below the whipstock from fluid communication with the deflected borehole. The slips are required to oppose the considerable thrust force upon the whipstock along the existing borehole axis and the torque force imposed by the deflected drill string rotation.
Although the whipstock deflects the bit cutting direction within the casing, that deflection simply turns the drill bit into the casing wall. Consequently, after the whipstock is set, it is then necessary to cut a window into the casing wall to facilitate advancement of the drill bit into the earth along the deflected direction. The window is cut by a steel milling tool at the end of the drill string. Following the milling tool can be one or more hole reaming tools to enlarge the casing window.
To avoid multiple xe2x80x9ctripsxe2x80x9d in and out of the borehole to perform the multiple operations required, the whipstock and packer/slip tools are combined with a casing mill and one or more reamers. The integrated combination is secured to the end of a drill string. The prior art provides a fluid conduit along the whipstock length to connect the drilling string pipe bore to the packer/slips. When the face of the whipstock deflection surface is directionally oriented, the packer and slips are engaged by fluid pressure supplied and controlled by surface pumps or, alternatively, by using the in situ hydrostatic pressure in the well bore applied against an atmospheric pressure chamber. The casing mill is disconnected from the upper end of the whipstock and lowered against the whipstock deflection surface while rotating to cut the casing window.
For directional orientation, the present state of the art relies upon telemetering technology characterized as xe2x80x9cmeasuring while drillingxe2x80x9d (MWD) or xe2x80x9clogging while drillingxe2x80x9d (LWD). Among other features and capacities, an MWD unit reports downhole characteristics of the drilling operation to a surface receiving unit. These downhole characteristics are reported as wireless (e.g. sonic) signal propagations transmitted, for example, along the column of drilling fluid within the associated drill pipe as the signal carrier medium. Circulating drilling fluid (i.e., mud) that is pumped downhole along the drill string tube bore drives a turbogenerator for signal generation energy. One of the characteristics reported by an MWD unit is the azimuth direction of the vertical plane that passes through the xe2x80x9chigh sidexe2x80x9d of the bore hole. Also reported is the borehole angle of departure from vertical. Knowing this geometry, the whipstock deflection surface may be accurately set in the desired direction relative to the xe2x80x9chigh sidexe2x80x9d plane direction.
One of the difficulties attendant to the prior art equipment and procedure as described above is the need for hydraulic connections between the drill string tubing bore and the whipstock packer/slip unit. As presently practiced, that connection comprises a boring along the length of the whipstock joint: an extremely difficult and expensive machining operation. At the upper end of the boring, the whipstock conduit is connected to the drill string with preformed or flexible tubing via a pressure set hydraulic valve. Both the tubing and the valve are vulnerable to malfunction and in-running damage.
It is, therefore, an objective of the present invention to provide a one-trip whipstock setting procedure that requires no hydraulic connection between the packer/slip unit and the drill string.
Another object of the present invention is a packer or slip setting procedure that is actuated by wireless MWD or LWD signals.
Also an object of the invention is a whipstock setting procedure that is faster and more reliable than prior art equipment and procedures.
A further object of the present invention is to use commonly used, state of the art equipment that is needed downhole to ascertain azimuth orientation of the drill string and whipstock deflection face to also activate the whipstock packer and/or anchor.
These and other objects of the invention are accomplished by a whipstock joint having a packer/slip unit disposed below the whipstock. The packer/slip unit may be actuated by in situ energy such as hydrostatic well pressure. The hydrostatic actuator for the packer/slip unit comprises a motor chamber for driving the packer and slip actuating pistons. Wellbore fluid flow through an internal conduit connected with the motor chamber is sealed by a solenoid valve. The solenoid valve is opened by a battery powered operating signal from a microprocessor. Opening of the solenoid valve admits in situ well bore pressure into the actuator motor chamber. The microprocessor is responsive to MWD or LWD transmitter signals but only in a preprogrammed sequence that may be controlled by selective operation of the tubing string mud flow.
As the one-trip whipstock equipment combination is run into the wellbore, drilling fluid (mud) is circulated down the drill pipe or coiled tubing bore to operate the MWD or LWD turbogenerator. When the desired whipstock deflection depth is found, the deflection surface is oriented by rotation of the drill string relative to the borehole highside azimuth as is reported by the MWD unit.
At this point, the drilling fluid pump or circulation control is operated in a predetermined manner to emit a distinctive signal pattern by the MWD transmitter. For example, the distinctive signal may be the absence of a signal transmission as the result of terminating the drilling fluid flow. Such distinctive signal pattern may be characterized as a reference or alert signal. Following the alert signal, the drilling fluid pump or flow control is operated in a further distinctive manner such as a programmed sequence of timed interval starts followed by timed interval stops, for example. The microprocessor that controls the packer/slip actuator is programmed to respond to the distinctive MWD signal transmission by emitting an operating power signal to the packer/slip solenoid valve. When the solenoid valve receives its power signal from the microprocessor, the valve opens to admit wellbore pressure into the packer/slip motor chamber. Resulting wellbore pressure entering the packer/slip motor chamber sets the whipstock packer and anchor slips. In a shallow well application, where the in situ pressure may be insufficient for packer or anchor setting, additional wellbore pressure may be applied externally to complete the setting procedure. From that point, the whipstock procedure continues in the manner known to the art.